1. Field of the Invention
The present invention relates to a display device including light emitting elements for display and more particularly, to a display device including a fan unit capable of preventing a temperature elevation due to heat generated by the emission of the light emitting elements.
2. Description of the Related Art
Recently, a display device using a plasma display, a liquid crystal display, a field emission display, a light emitting diode (hereinafter, referred to as the LED appropriately) or the like is widely known in general in a field of the display device, and it is increasingly employed together with a conventional display device using a CRT (Cathode Ray Tube) or a discharge tube, or instead of this.
However, according to the above display device, since its light conversion efficiency is low and it is about 10% in the case of the LED element, it means that a most part of supply power is converted to heat. When the element temperature is increased, since the light conversion efficiency is further lowered, it is required to prevent the temperature of the element from increasing with some cooling measures. In addition, when the element temperature is lowered, the element deterioration can be prevented and the reliability can be enhanced over a long period of time.
Especially, in the case of the display device using the light emitting element such as the LED element, unlike the one using the conventional CPU and the like, elements to be a light emitting source, that is, a heat generating source are arranged almost all over the surface of the display device at certain intervals in general. And the whole surface of the display device must be cooled uniformly. When the substrate on which the light emitting elements are arranged is partially cooled, the element temperature is largely lowered only at a part having high cooling efficiency due to said cooling and the light conversion efficiency of the element is partially raised, which causes color unevenness. Therefore, in this case, the functionality as the display device is degraded.
As a method to cool the display device using the LED element, as described in a patent document 1 (Japanese Patent Laid-open Publication No. 10-293540: refer to paragraph [004] thereof), a method for releasing heat to the outside by thermal conduction of a lead terminal of the LED is used in general. However, when the display device is set outdoors, the lead terminal is molded with a resin and the like to be waterproof, so that the heat releasing effect of the lead terminal is reduced. In this case, cooling down a LED mounted substrate itself is an only method to lower the temperature.
Therefore, according to the display device disclosed in the above patent document 1, as to a display unit having a LED mounted substrate which is molded with a resin and the like, the heat of the LED mounted substrate is removed by forming a ventilation hole so as to penetrate the display unit from its front to back surface, and sending wind from blowing means to the ventilation hole.
In addition, although several number of the above-described display units are arranged in an actual display panel to implement large-sized screen, according to the display device disclosed in the above patent document 1, a power supply is provided outside the display unit. In this case, the thermal effect of the heat from the power supply to the substrate can be easily avoided.